Brushless motors revolutionized the unmanned aerial systems (quadcopters, "drones") because of their high torque, nearly infinite controllability and overall efficiency. A typical control system uses an ESC (Electronic Speed Controller) that simply applies power to the stator electromagnets in succession to cause rotation. If this is a square wave, as is often the case, it can produce rather a lot of radio interference as well as minor mechanical stresses. Top of the line DJI control technique is to use a pulse-width modulated current that effectively ramps up the current on each stator magnet which eliminates radio interference and the vibration that accompanies electronic commutation by square wave controllers.
Brushless motors revolutionized the unmanned aerial systems (quadcopters, "drones") because of their high torque, nearly infinite controllability and overall efficiency. A typical control system uses an ESC (Electronic Speed Controller) that simply applies power to the stator electromagnets in succession to cause rotation. If this is a square wave, as is often the case, it can produce rather a lot of radio interference as well as minor mechanical stresses. Top of the line DJI control technique is to use a pulse-width modulated current that effectively ramps up the current on each stator magnet which eliminates radio interference and the vibration that accompanies electronic commutation by square wave controllers.